The Balleny Island hydrophone array: Hydro-acoustic records of sea-ice dynamics, seafloor volcano-tectonic activity, and marine mammal vocalizations off Antarctica

An array of 5-hydrophone moorings was deployed north of the Balleny Islands, a chain of subaerial/submarine volcanoes located near the Ross Sea, Antarctica. The acoustic records are dominated by broadband, short duration icequake signals created by the impact and breakup of sea-ice in the region. Spectral records of icequakes show sea-ice breakup is a maximum during the austral summer-fall months, and lowest during the late-winter spring months, consistent with seasonal freeze-thaw cycles. The hydrophones records also contain short-duration (30 sec), low-frequency (100 Hz) signals of harmonic tremor with multiple overtones that are likely caused by the grounding of large icebergs on the Antarctic continental shelf. Several hundred earthquakes were also recorded by the hydrophone array. The largest earthquakes (4.3–6.1 mb) occurred on the Pacific-Antarctic Ridge north of the Balleny Islands. Source bearing information indicates several small earthquakes were also detected from the Balleny Islands, however accurate event locations are not yet available. The vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectral records in the 15–28 and 89 Hz bands. In addition, the vocalizations of leopard seals (Hydrurga leptonyx) are observed in the 200–400 Hz band during the austral spring months of 2015.